So far this game is awesome, but I still think it's impossible for it to top the masterpiece that is Bioshock 1. I'm not that far though.

I loved the creepiness of it. Wandering around in a pitch black room, you turn around and barely make out the outline of somebody/something just standing there. Is it alive? Does it see me? Then it attacks. Playing that game at night in a dark room, I nearly jumped out of my chair a couple of times. Very effective.